语法填空（共10小题，每小题1.5分，满分15分）
If you walked past the supermarket, you would find many foods that have been treated (kill) any harmful germs that might have been in them. Milk is a good example. Raw milk --- that is, milk just as it comes from the cow --- may be (safe) to drink. But the milk is heated and then cooled, the harmful germs are killed. The man discovered this way of treating milk was a Frenchman by the name of Louis Pasteur.
In the supermarket you would also find many frozen foods --- frozen fruits, vegetables, meat and fish. As techniques for (freeze) food are being improved, more frozen foods are appearing on the market, and more people are buying them. Fruits and vegetable to be sold in the supermarket are often frozen the moment are picked. The fruits and vegetable are frozen, the better. machines are often taken into the fields where food grows, so that little time is lost picking and freezing.